In many types of dispensers it is for various reasons often desirable to provide a dispenser part where at least an outer surface, a shell or a similar dispenser part is made from two similar or different plastic materials. For instance, it is possible to make one section of the dispenser part transparent, in order to facilitate checking of the level of a consumable product contained within the dispenser. A second section can be made opaque in order to hide a dispensing mechanism, to allow monitoring of the filling level and to provide a dispenser with an aesthetically pleasant appearance.
When making such a dispenser part, the first component is usually injection moulded in a first mould and transferred to a second mould to be joined by a subsequently injected component. A dispenser part manufactured in this way may have problems with distortion of at least the first component, as well as of the seam, in particular in or near the regions of the side edges. The component parts are usually joined end-to-end and even with local reinforcements, the seam may lack sufficient strength to withstand the forces it may be expected to withstand. For example, the front of the dispenser may be exposed to accidental or intentional point loading, such as an impact force caused by an object or a person striking the dispenser. A weak seam may cause the dispenser part making up the cover to crack along at least part of the front surface, requiring the dispenser part to be replaced.
Various methods for manufacturing injection moulded products are known from various prior art documents. WO 98/02361 relates to a known overmoulding process, wherein a first component (a preform) is injected into a first mould. The preform is then transferred into a second mould, wherein a second material is injected and overmoulded onto the perform to form a finished product, wherein the materials are joined along a continuous, circular seam. Johannaber/Michaeli “Handbuch Sprizgiessen, 6-Sonderverfahren der Spritzgiesstechnologie”, Carl Hanser Verlag, Munich, Del., is a handbook on injection moulding. Selected pages from this handbook relates to methods for overmoulding. JP 03-120022 shows a conventional overmoulding process, where two components are placed in a mould and joined by injection moulding an additional material in a gap between the said components.
The object of the invention is to provide an improved dispenser part and method for making it, in order to solve the above problems relating to the distortion of the dispenser part and the strength of the seam.